Turbine Having Compact Inflow Housing Thanks to Internal Control Valves

ABSTRACT

A turbine having an inflow housing is provided. The turbine includes an inlet for an inflowing working fluid, wherein the inlet can be closed by a quick closing valve, a plurality of control valves and at least two nozzle groups. The flow of the working fluid is controllable by the inlet into the nozzle groups via the control valves. Furthermore, the inlet can be connected via an inlet line to the first nozzle group, wherein the inlet line is guided through the primary control valve such that the flow of the working fluid along the inlet line can be controlled using the primary control valve. The secondary control valve connects the first nozzle group to the second nozzle group such that the flow of the working fluid from the first nozzle group into the second nozzle group may be controlled using the secondary control valve.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is the US National Stage of International Application No. PCT/EP2008/055045, filed Apr. 25, 2008 and claims the benefit thereof. The International Application claims the benefits of European Patent Office application No. 07011268.5 EP filed Jun. 8, 2007, both of the applications are incorporated by reference herein in their entirety.

FIELD OF INVENTION

The present invention relates to a turbine with an inflow housing which comprises an inlet for an inflowing working fluid, wherein the inlet can be closed by a quick closing valve, a plurality of control valves and at least two nozzle groups, the flow of the working fluid being controllable from the inlet into the nozzle groups via the control valves.

BACKGROUND OF INVENTION

This type of turbine is known from the publication DE 1 915 267 A1 of the same applicant. The inflow housing is the part of the turbine housing into which the working fluid flows into the turbine and in which the working fluid is directed onto the rotor. For applying the fluid to the rotor the inflow housing has a number of nozzle groups which extend in the shape of a ring sector at a common diameter around the rotor. Each nozzle group combines a number of nozzles which are directed onto the rotor. The inflowing working fluid flowing in through the inlet is directed into the nozzle groups, exits from the nozzles and flows through the rotor blading. The division of the nozzles into nozzle groups is used for power regulation. Since the mass throughput is restricted by the nozzle cross section, the overall mass throughput and thereby the power of the turbine can be controlled by variation of the nozzle groups to which the working fluid is applied. The distribution of the working fluid to the individual nozzle groups and the individual mass throughput per nozzle group is controlled by the control valves. A quick closing valve is provided for an emergency shutdown which closes off the inlet and can therefore suppress the overall flow through the turbine.

The inflow housing of a known steam turbine is shown in FIG. 2 a of DE 1 915 267 A1. With the housing design basically still manufactured today the control valves are located in what is referred to as a valve housing or valve compartment above the actual turbine housing. The working fluid flows in laterally through an inlet, passes through a quick closing valve and reaches the valve compartment from which five parallel-switched supply lines above a control valve in each case branch off to nozzle groups. Each valve group thus has its own supply line available to it and a separate control valve. The respective feed lines and valves are connected in parallel. The enclosed FIG. 1 shows a circuit diagram of this arrangement. With current designs of such a valve arrangement the linearly-guided valve spindles of the control valves are each driven with an individual motor and not, as shown in this publication, via a control bar.

In another known design of steam turbines the control valves are arranged outside the turbine housing and linked via welded-on pipes or pipe bends to the nozzle housing. The fresh steam flow divided up remotely from the inflow housing is thereby guided through the comparatively long pipes to the nozzle groups.

However both designs have the disadvantage that the inflow housing with the external valve compartments or the pipes occupy a great deal of space. In addition these constructions are very costly, since very high-quality materials must be used for the cast housings of the valves, pipes and flanges. The many diversions of the flow in the pipes or in the supply pipes to the nozzle groups inevitably lead to significant energy losses. In addition the control valves described in DE 1 915 267, through which the flow is axial, also demand high setting forces.

SUMMARY OF INVENTION

In respect of this prior art the present invention is based on the object of developing a turbine of the type described at the outset so that its inflow housing is as compact a design as possible, and that the flow losses caused by long lines are reduced. This object is achieved first of all by the control valves being functionally divided into a primary control valve and at least one secondary control valve. Furthermore the inlet is to be connected to the first nozzle group via the inlet line, whereby the inlet line is to be guided through the primary control valve such that the flow of the working fluid along the inlet line is able to be controlled by means of the secondary control valve. In accordance with the invention the secondary control valve connects the first nozzle group to the second nozzle group such that the flow of the working fluid from the first nozzle group and the second nozzle group is able to be controlled by means of the secondary control valve. The present invention is based on the underlying idea of no longer controlling individual nozzle groups with control valves connected in parallel, but of connecting the nozzle groups in series via the secondary control valves. This measure basically allows savings to be made in pipe runs in the inflow housing and thus to achieve a more compact construction. The flow losses are also reduced by the savings in pipes. The valve control of a primary control valve is decisive in the control of turbine since this can control the entire flow of the working fluid through the turbine. Since the first nozzle group is connected directly to the inlet via the primary control valve and the quick closing valve working fluid is always applied to the first nozzle group when the primary control valve and the quick closing valve are open. To increase the power, the subordinate nozzle groups are successively switched in by the secondary control valves.

A preferred development of the invention makes provision for at least three nozzle groups connected in series to be provided in the inflow housing, so that at least two secondary control valves are necessary that connect the first nozzle group to the second or the second nozzle group to the third. To enable the power to be controlled in even smaller steps, it is also recommended that an additional fourth or fifth nozzle group be provided; the number of secondary control valves necessary would consequently increase to three or four.

As already mentioned the entire flow of the working fluid flows to the primary control valve. To keep the actuation forces low and to allow a soft start-up of the turbine, it is recommended that this valve being equipped with a pilot valve.

The starting up of such a turbine is preferably undertaken by the following steps: With the turbine at rest the quick closing valve is initially opened which causes the pressure of the working fluid to build up as far as the valve seat of the primary control valve. The first nozzle group is activated directly by the primary control valve. With the aid of a small pilot valve on the primary control valve the turbine is initiated and brought up to its operating speed. After the machine has accepted a load and the first nozzle group has been fully activated, the main control valve is started and thus releases the entire cross-section for the overall mass flow of the working fluid. Since the mass throughput is capped by the valve cross sections of the first group, the power of the turbine remains constant on reaching the maximum mass throughput. If the power of the turbine is to be increased further, the first secondary control valve is opened so that the flow now also reaches the second nozzle group. This increases the mass throughput. Provided the turbine has available to it further downstream nozzle groups, these will be switched-in later by opening the respective secondary control valves.

The inventive circuit of the individual nozzle groups allows the shut-off facilities of the secondary control valves to be arranged directly between the nozzle groups extending in the shape of a ring sector around the rotor, i.e. at the same radius as the nozzle groups. The flow paths in the inflow housing are further shortened in this way.

The space occupied by the inflow housing can be significantly reduced in this design by the axes of actuation of the secondary control valves being arranged radially to the axis of rotation of the rotor. The actuation path of the shut-off facilities is then not actually located tangentially to the diameter of the nozzle groups, but radially. The necessary external diameter of the inflow housing is reduced in this way.

Preferably in this embodiment the shut-off facilities of the secondary control valves are designed as rotationally-switchable control flaps so that the actuation axis involved is an axis of rotation. The rotationally-switched shut-off facilities occupy less space than the linearly-switched shut-off facilities, require lower actuation forces and do not have to be completely sealed. The use of rotationally-switched, not completely sealed shut-off facilities is also possible since no quick closing function is required for the secondary control valves. This quick closing function is performed by the quick closing valve and the downstream primary control valve. Preferably the inflow housing of the inventive turbine is an essentially annular design and is subdivided into at least two housing halves, with the inlet line being an integral component of a housing half. The advantage of this embodiment is that the line of the working fluid can be welded on without a flange connection, that only one entry into the turbine housing must be sealed off with the piston ring and that all components warm up well during the start of phase. With a large volume of steam the two housing halves can each be provided with an integrated inlet in order to double the normal width of the inlet steam connection overall.

The present invention is preferably employed in the area of axial designs of steam turbine.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be explained in greater detail with reference to an exemplary embodiment. The figures show:

FIG. 1: a conventional valve circuit (prior art);

FIG. 2: an inventive valve circuit;

FIG. 3: an inflow housing in a part-exploded perspective view;

FIG. 4: an inflow of housing in a part-exploded rearview;

FIG. 5: a section through the inflow housing;

FIG. 6: an inflow housing with two inlets.

DETAILED DESCRIPTION OF INVENTION

FIG. 1 shows a schematic diagram of the last circuit of a conventional steam turbine, as is known from the publication mentioned at the start. The housing of the turbine comprises an inflow housing 1 in which the rotor not shown in the diagram is supported to allow rotation. The rotor has working fluid applied to it via four nozzle groups 21, 22, 23, 24 which extend in the shape of an annular sector on a common diameter D around the rotor.

The working medium—steam in the case of a steam turbine—flows through an inlet 3 into the inflow housing 1. Directly behind the inlet 3 is arranged a quick closing valve 4 through which the inlet 3 can be rapidly closed in an emergency. Behind the quick closing valve 4, the flow fans out in four supply lines 51, 52, 53, 54 which connect the inlet 3 with the nozzle groups 21, 22, 23, 24 in each case. The flow of the working fluid through the supply lines 51, 52, 53, 54 is controlled by respective control valves 61, 62, 63, 64. The nozzle groups 21 through 24 are consequently connected in parallel via their respective supply lines 51 through 54 and the associated control valves 61 through 64.

The inventive circuit is shown in FIG. 2. Here the inlet 3 (fresh steam connection) able to be closed off via the quick closing valve 4 is connected via an inlet line 7 directly and exclusively to the first nozzle group 21. The inlet line 7 is routed through the primary control valve 8 which controls the overall flow through the turbine. The primary control valve 8 is advantageously equipped with a pilot valve which can be realized for example by a pilot valve connected in parallel (not shown in the diagram). Quick closing valve 4, primary control valve 8 and first nozzle group 21 are thus connected in series via the inlet line 7. The series circuit continues into the second to 22, third 23 and fourth nozzle group 24. The second nozzle group 22 is connected to the first nozzle group 21 exclusively via a first secondary control valve 91. The connection of the second nozzle group 22 to the third nozzle group 23 is made in the same way via a second secondary control valve 92, the connection into the fourth nozzle group 24 is made accordingly via a third secondary control valve 93.

The shut-off facilities 10 of the secondary control valves 91, 92, 93 are located on the same diameter D as the nozzle groups 21, 22, 23, 24. In this way an especially compact design of the inflow housing 1 is achieved. The axes of actuation 11 of the secondary control valves extend radially to the axis of rotation of the rotor, i.e. the center of the housing. Through these measures the setting motors 12 of the actuation facilities can be arranged outside the inflow housing 1.

Concrete proposed layouts of this design can be seen in FIGS. 3 through 5. The secondary control valves 91, 92, 93 are to be activated rotationally here so that the shut-off facilities 10 are rotary flaps. The setting motors 12 are placed on the inflow housing 1, i.e. in the pressure-free area. Only the axis of actuation left in the housing 11 must be sealed, which is easy to do with axes of rotation.

The inflow housing 1 itself is therefore essentially annular and far more compact than in the prior art since it merely accommodates the nozzle groups 21, 22, 23 and the shut-off facilities 10.

The inflow housing 1 is cast and divided up into and upper housing half 1 a and a lower housing half 1 b, with the inlet line 7 being an integral component of the lower housing half 1 b. Primary control valve 8 and quick closing valve 4 are arranged outside the housing 1. Thus only one steam feed into the turbine housing is to be sealed with piston rings. The steam line can thus be welded on without a flange connection.

With a very large volume of steam it is likewise possible to provide the inflow housing with two inlet lines, in order to double the nominal width of the inflowing steam connection in this way. Two primary control valves and two quick closing valves are then accordingly also required, one for each inlet. FIG. 6 shows and inflow housing with two integrated inlet lines 7.

As well as the compact dimensions and the lower flow losses, a particular advantage of the construction shown lies in the lower setting forces of the valves. Thus especially the inner control flaps only need small setting forces and especially no quick closing facility since they are connected in series with the primary control valve 8 and the quick closing valve 4. In addition the inner control flaps can be removed and replaced without opening the turbine housing. 

1.-10. (canceled)
 11. A turbine with an inflow housing, comprising: an inlet for an inflowing working fluid, the inlet may be closed off by a quick closing valve; a plurality of control valves; and at least two nozzle groups, wherein the flow of working fluid may be controlled from the inlet into the plurality of nozzle groups using the plurality of control valves, wherein the inflow housing includes a primary control valve and at least one secondary control valve, wherein the inlet is connected via an inlet line to a first nozzle group, wherein the inlet line is routed through the primary control valve such that the flow of working fluid along the inlet line may be controlled using the primary control valve, and wherein a first secondary control valve connects the first nozzle group to the second nozzle group such that the flow of the working fluid from the first nozzle group into the second nozzle group may be controlled using the first secondary control valve.
 12. The turbine as claimed in claim 11, further comprising a third nozzle group and a second secondary control valve, wherein the second secondary control valve connects the second nozzle group to the third nozzle group such that the flow of working fluid from the second nozzle group into the third nozzle group may be controlled using the second secondary control valve.
 13. The turbine as claimed in claim 11, wherein the primary control valve is equipped with a pilot valve.
 14. The turbine as claimed in claim 11, wherein the turbine further comprises a rotor supported to allow rotation in the inflow housing, wherein the plurality of nozzle groups extend in a shape of a ring sector at a common diameter around the rotor, wherein each secondary control valve includes a shut-off facility and an axis of actuation, and wherein the shut-off facilities of the plurality of secondary control valves are arranged on the diameter of the plurality of nozzle groups.
 15. The turbine as claimed in claim 14, wherein the axes of actuation of the plurality of secondary control valves extend radially to a first axis of rotation of the rotor.
 16. The turbine as claimed in claim 15, wherein the shut-off facilities of the plurality of secondary control valves can be switched rotationally so that the axis of actuation involved is a second axis of rotation.
 17. The turbine as claimed in claim 14, wherein the inflow housing is essentially annular and is divided into at least two housing halves, and wherein the inlet line is an integral component of a first housing half.
 18. The turbine as claimed in claim 11, wherein each nozzle group is provided with a plurality of nozzles directed onto the rotor, and wherein the plurality of nozzles are directed axially onto the rotor so that the flow of working fluid through the turbine is in parallel to the first axis of rotation.
 19. The turbine as claimed in claim 11, wherein the inflowing working fluid is steam.
 20. The turbine as claimed in claim 11, further comprising a fourth nozzle group and a third secondary control valve, wherein the third secondary control valve connects the third nozzle group to the fourth nozzle group such that the flow of working fluid from the third nozzle group into the fourth nozzle group may be controlled using the third secondary control valve.
 21. A method for operating a turbine with an inflow housing, comprising: opening a quick closing valve, the quick closing valve is used to quickly close off an inlet for a working fluid flow; opening a pilot valve of a primary control valve; finish opening the primary control valve after the operating speed of the rotor is reached; and opening the first secondary control valve, wherein an inlet line is routed through the primary control valve such that the working fluid flow along the inlet line may be controlled using the primary control valve, and wherein the first secondary control valve connects a first nozzle group to a second nozzle group such that the working fluid flow from the first nozzle group into the second nozzle group may be controlled using the first secondary control valve.
 22. The method as claimed in claim 21, wherein the method is used during a start-up of the turbine.
 23. The method as claimed in claim 21, further comprising a third nozzle group and a second secondary control valve, wherein the second secondary control valve connects the second nozzle group to a third nozzle group such that the flow of working fluid from the second nozzle group into the third nozzle group may be controlled using the second secondary control valve.
 24. The method as claimed in claim 21, wherein the primary control valve is equipped with a pilot valve.
 25. The method as claimed in claim 21, wherein the turbine further comprises a rotor supported to allow rotation in the inflow housing, wherein the plurality of nozzle groups extend in a shape of a ring sector at a common diameter around the rotor, wherein each secondary control valve includes a shut-off facility and an axis of actuation, and wherein the shut-off facilities of the plurality of secondary control valves are arranged on the diameter of the plurality of nozzle groups.
 26. The method as claimed in claim 25, wherein the axes of actuation of the plurality of secondary control valves extend radially to a first axis of rotation of the rotor.
 27. The method as claimed in claim 26, wherein the shut-off facilities of the plurality of secondary control valves can be switched rotationally so that the axis of actuation involved is a second axis of rotation.
 28. The method as claimed in claim 25, wherein the inflow housing is essentially annular and is divided into at least two housing halves, and wherein the inlet line is an integral component of a first housing half.
 29. The method as claimed in claim 21, wherein each nozzle group is provided with a plurality of nozzles directed onto the rotor, and wherein the plurality of nozzles are directed axially onto the rotor so that the flow of working fluid through the turbine is in parallel to the first axis of rotation.
 30. The method as claimed in claim 21, wherein the inflowing working fluid is steam. 